bcachefs: Fix invalid shift in validate_sb_layout()

bcachefs: Fix invalid shift in validate_sb_layout()

Add check on layout->sb_max_size_bits against BCH_SB_LAYOUT_SIZE_BITS_MAX
to prevent UBSAN shift-out-of-bounds in validate_sb_layout().

Reported-by: syzbot+089fad5a3a5e77825426@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=089fad5a3a5e77825426
Fixes: 03ef80b469d5 ("bcachefs: Ignore unknown mount options")
Tested-by: syzbot+089fad5a3a5e77825426@syzkaller.appspotmail.com
Signed-off-by: Gianfranco Trad <gianf.trad@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>